Most notably, it was recently discovered that a GGGGCC hexanucleotide repeat expansion in the first intron of the C9orf72 gene is the most common genetic cause of ALS pathogenesis, more common than all other known ALS gene mutations combined, accounting for between 37%–50% of familial ALS cases among studied cohorts [190,191,192,193,194,195,196,197]. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.